Mechanical aids for the transport of objects are among the oldest examples of human innovation. The Pyramids of Giza, Stonehenge, and the statues of Easter Island are just a few of the ancient human-built structures built using such aids including wedges, a track of logs and perhaps pulley-type devices to transport large stones from the quarry to the building site, often over many miles. The earliest example of the wheel, discovered in Mesopotamia, dates to about 3500 B.C.
Even more sophisticated devices for the transport of objects and people have revolutionized and changed the world and altered its landscape. Boats, wagons, sledges, trains, automobiles and airplanes all have the fundamental object to carry objects (or people) over long distances. Mechanical aids such as wheelbarrows, carts, forklifts and the like are designed for carrying objects or material over shorter distances.
One device having a diverse utility for the relatively short distance transport of objects ranging from boxes and crates to furniture is the “hand truck”. This device generally consists of a wheeled apparatus having an L-shaped side profile, with wheels located at the vertex of the angle forming the “L” shape, such angle being approximately 90 degrees. The horizontal portion of the L is generally considerably shorter than the vertical portion. Both horizontal and vertical portions of the hand truck are made from one or more rigid material such as a metal or metal alloy (e.g., steel, bronze, iron, aluminum and the like), but may comprise a sufficiently hard wood, plastic, composite (such as a carbon composite) or other material. When the vertical portion of the L-shaped hand truck profile is viewed from the rear it generally comprises two upwardly extending lateral arm members, with each lateral arm member terminating in a handle. The upwardly extending lateral arms are rigidly connected by, for example, at least two reinforcing horizontal members which provide mechanical strength and resistance to twisting and separating forces placed on the lateral arm members during use.
The horizontal portion of the L is generally a substantially flat plate of material and, in side profile extends outward from the vertex of the angle forming the L shape. The width of the horizontal portion is generally approximately the distance between the arm members of the vertical portion of the L, and also is made from a sufficiently hard and rigid material to be subject to forces in for example, the hundreds of pounds. A particular feature of this kind of hand truck is that the L shape and strong construction of the device result in the hand truck constituting a lever, with the vertical portion of the L being a relatively long lever arm. When the flat horizontal member of the hand truck is slid under an object to be transported and the vertical member is then brought towards a horizontal position using the vertex of the L as a fulcrum, the object is lifted from the ground and is supported by both the vertical and horizontal portions of the hand truck. Furthermore, since the wheels of the hand truck are situated at, and extend slightly below the vertex of the L, when the object is lifted, most of the weight of the object rests on the wheels, with only a portion of this weight being supported by the person or persons holding the handles of the vertical portion of the hand truck. The object can thus easily be wheeled to a location, the vertical portion again allowed to assume a vertical position, and the horizontal portion of the hand truck slid from under the object to complete the transport.
As can be seen, the hand truck is a very versatile device that permits the transport of multiple and/or moderately heavy objects that could otherwise not be moved by a single person. For this reason, hand trucks are ubiquitously used in warehouses, by furniture movers and the like. However, this device does have limitations.
For example, the short horizontal portion of the hand truck typically only supports a portion of the object to be transported. This requires the object to be transported to have sufficient internal rigidity or cohesiveness to be able to support a portion, often a large portion, of its own weight itself. If the object is large or its weight is not adequately balanced (for example, an appliance such as a refrigerator, stove or similar object), it must be fastened to the vertical portion of the dolly, such as by using straps. However, straps generally only hold the object solidly against the vertical portion; they typically do not provide substantial lateral support unless the object is wide and rigid enough to fit and be supported by the fastener straps. Of course, if the object is too large, the straps may not be sufficiently long to retain or support the object.
Additionally if the object to be transported is, for example, narrow and/or long or wide in shape (i.e., extending outward along the plane of the horizontal portion of the L-shape of the hand truck in side profile), a hand truck is also imperfectly effective. The hand truck lacks sufficient lateral support to prevent the narrow object from sliding off the hand truck or flopping from side to side during transport. Additionally, proper and secure alignment of an object on a hand truck during transport is far more difficult when the object is long and/or narrow as compared to an object that is, for example, wide and short.
Also, even if the weight of the object is evenly distributed, if it is sufficiently long, the majority of the mass of the object extends beyond the supporting plate of the horizontal portion of the hand truck. If the object is rigid and long enough, the lever arm of the horizontal portion of the hand truck is thereby lengthened, causing it to exert a greater force on the vertical portion of the hand truck, resulting in a resistance to the downward force placed on the vertical portion when it tipped downward into a “transport” position. In extreme cases the hand truck is ineffective because the lever advantage of the system is reversed when the length of the lever arm of the load exceeds that of the vertical portion.
Oddly sized objects that lack sufficient rigidity (such as a mattress) are also difficult to transport using a hand truck. As stated above, a hand truck provides virtually no side (lateral) support and relies on straps to provide resistance to a shift in the lateral position of the object. However, if the object cannot be strapped tightly without bending, folding or deforming the object, the straps or other retaining means may not be able to provide sufficient resistance against such a shift.
In particular, objects such as materials in sheet form, for example wood sheets, metal sheets, dry wall, and the like cannot easily be transported using a hand truck. Similarly, objects including bed mattresses, tabletops, mirrors and plate glass are not generally amenable to easy transport using a hand truck, particularly if parts of the transport route are narrow (such as doorways and halls) and cannot accommodate such objects being loaded “sideways” on the hand truck.
Several attempts have been made to devise alternative transport apparatus suitable for the transport of objects that are not easily moved using the traditional hand truck. Thus, U.S. Pat. No. 4,166,638 discloses a platform having 4 caster wheels and fitted with straps for moving items of furniture. This platform is not disclosed as having any lateral or vertical support.
U.S. Pat. No. 5,863,056 discloses a mattress moving system, said to be performable by one person, consisting of a single horizontal strap with detachable handles to which are fastened a pair of vertical straps, each one having an expandable, detachable and adjustable castered platform having wheels for rolling the mattress in an upright position, standing on edge. The mattress must first be affixed with the straps (which requires affixing the vertical straps to the horizontal strap), the horizontal strap placed on the mattress while it is lying on one side, then stood on one edge and the vertical straps affixed by raising first one then the other end of the mattress. This system appears to require substantial work to prepare the mattress for transport and does not readily address the problem, seen with many mattresses, that the mattress droops or sags when stood on an edge without adequate lateral support.
U.S. Pat. No. 6,085,370 describes a device for carrying a mattress comprising a mattress cover affixed to the surface of the mattress using a bungee-type cord and handles integrated into the cover. The handles are used to facilitate moving the mattress, which it appears would be most easily transported by more than one person.
U.S. Pat. No. 6,979,035 is drawn to an apparatus to assist in the manual transport of large, heavy, or unwieldy objects comprising a strap with two cradle assemblies which fit under and support the mattress and a handle at each end of the strap to facilitate carrying the mattress. However, at least two persons (one on each side of the mattress) are required to use this device, and the full weight of the load is borne by the movers.
Thus, there exists a continuing need for apparatus and methods for the transport of objects, particularly although not necessarily exclusively, objects such as materials in sheet form, for example wood sheets, metal sheets, dry wall, and the like, as well as narrow objects such as bed mattresses, tabletops, mirrors and plate glass and the like.